1. Field of the Invention
The present invention relates to liquid organic concentrates permitting the preparation of biocidal aqueous microemulsions useful for the protection of freshly felled and sawn timber, and to the aqueous microemulsions produced by adding water to such concentrates. This invention also relates to the use of such microemulsions for ensuring the protection of freshly felled and sawn timber, at least against the fungal deep blue stain of timber and the development of surface moulds thereon.
2. Description of the Prior Art
Protecting or preserving timber by impregnating it, e.g., by soaking or spraying it with fungicidal and/or insecticidal substances has long been known to this art. The active substance, preferably one that is water-insoluble, is dissolved, for example, in a suitable liquid medium to form a concentrate. The dissolving medium usually comprises one or more organic solvents for the active substance, mixed, if desired, with one or more oils and/or with one or more fixing agents. At the point in time of its use for impregnating the timber to be treated, the liquid concentrate is diluted with water and stirred so as to form an emulsion, and it is this emulsion which is definitively applied onto the surface to be treated.
Fresh timbers abound in sap which is rich in easily assimilable substances which create a nutrient medium for various biological organisms including, in particular, the agents responsible for fungal blue stain and agents responsible for moulds. The agents responsible for blue stain consist particularly of cellulolytic imperfect fungi which can develop quickly and enter deeply into the cells of the timber cores and whose mycelium is dark in color. While the damage produced has no detrimental effect on the physical and mechanical properties of the timber, on the other hand, the aesthetic qualities of the sapwood are greatly altered. Exemplary of such fungi are Aureobasidium pullulans, Sclerohoma piytohila and Hormonema dematioides. The agents responsible for moulds in this case also consist particularly of imperfect fungi, generally cellulolytic, which develop on the surface of the timber in moist conditions such as those encountered in countries with a temperate climate, producing fruiting organs of various shapes and colors, which are detrimental to the aesthetic appearance of the timber. Exemplary of such fungi are Aspergillus spp, Trichoderma spp, Penicillium spp and Cladosoorium spp.
Good temporary fungicidal protection of fresh timber requires the availability of a treatment formulation:
(i) containing oen or more fungicidal active agent(s) capable of combating the attack by fungi responsible for the deep blue stain and the surface moulds, and
(ii) exhibiting a twofold behavior; a first behavior according to which the treatment product must be able to effect penetration of the timber by th fungicidal substance(s) provided for combating the attack by the organisms responsible for the blue stain; and a second, simultaneous behavior, according to which the treatment product must be capable of creating, at the same time, an antimould surface barrier while allowing the fungicidal substance(s) intended for combating the attack of the organisms responsible for moulds to be maintained at the surface of the timber.
Belgian Patent BE-A-904,660 describes a fungicidal aqueous emulsion obtained by diluting, with water, a concentrate based on two fungicidal substances and an appropriate solvent for these fungicides. The fungicidal substances employed are: on the one hand, a derivative of imidazole or of 1,2,4-triazole and, on the other hand, a quaternary ammonium salt derived from an organic or inorganic acid. An emulsion of this type, prepared from a concentrate containing, for example, lH-1-[2-(2,4-dichlorophenyl)-1,3-dioxolanyl-2-methyl]-1,2,4-triazole (known as azaconazole) and benzalkonium chloride as fungicidal substance, has been found to be advantageous because it enables the fungicidal substances to penetrate into the timber quite deeply (probably by virtue of the surfactant effect which the quaternary ammonium salt can also develop); on the other hand, it is found that this emulsion does not provide an effectively antimould barrier at the surface of the timber.